1. Field of the Disclosure
Embodiments disclosed herein generally relate to apparatuses and methods for cleaning tubing used in downhole environments. More specifically, apparatuses and methods disclosed herein may be used in cleaning casing used in connection with oil and gas wells.
2. Background Art
Hydrocarbons (e.g., oil, natural gas, etc.) are obtained from a subterranean geologic formation (i.e., a “reservoir”) by drilling a wellbore that penetrates the hydrocarbon-bearing formation. In order for the hydrocarbons to be produced, that is, travel from the formation to the wellbore, and ultimately to the surface, at rates of flow sufficient to justify their recovery, a sufficiently unimpeded flowpath from the subterranean formation to the wellbore, and then to the surface, must exist or be provided.
Subterranean oil recovery operations may involve the injection of an aqueous solution into the oil formation to help move the oil through the formation and to maintain the pressure in the reservoir as fluids are being removed. The injected aqueous solution, usually surface water (lake or river) or seawater (for operations offshore), generally contains soluble salts such as sulfates and carbonates. These salts may be incompatible with the ions already contained in the oil-containing reservoir. The reservoir fluids may contain high concentrations of certain ions that are encountered at much lower levels in normal surface water, such as strontium, barium, zinc and calcium. Partially soluble inorganic salts, such as barium sulfate (or barite) and calcium carbonate, often precipitate from the production water as conditions affecting solubility, such as temperature and pressure, change within the producing wellbores and topsides. This is especially prevalent when incompatible waters, such as formation water, seawater, or produced water, encounter soluble inorganic salts.
A common reason for a decline in hydrocarbon production is the formation of scale in or on the wellbore, in the near-wellbore area or region of the hydrocarbon-bearing formation matrix, and in other pipes or tubing. Oilfield operations often result in the production of fluid containing saline-waters as well as hydrocarbons. The fluid is transported from the reservoir via pipes and tubing to a separation facility, where the saline-waters are separated from the valuable hydrocarbon liquids and gasses. The saline-waters are then processed and discharged as waste water or re-injected into the reservoir to help maintain reservoir pressure. The saline-waters are often rich in mineral ions such as calcium, barium, strontium and iron anions and bicarbonate, carbonate and sulphate cations.
Generally, scale formation occurs from the precipitation of minerals, such as barium sulfate, calcium sulfate, and calcium carbonate, which become affixed to or lodged in the pipe or tubing. When the water (and hence the dissolved minerals) contacts the pipe or tubing wall, the dissolved minerals may begin to precipitate, forming scale. These mineral scales may adhere to pipe walls as layers that reduce the inner bore of the pipe, thereby causing flow restrictions. Not uncommonly, scale may form to such an extent that it may completely choke off a pipe. Oilfield production operations may be compromised by such mineral scale. Therefore, pipes and tubing may be cleaned or replaced to restore production efficiency.
Generally, operations to clean downhole tubing include the use of scrapers to remove debris from the inside surface of the tubes. Debris, in addition to scale deposits as discussed above, may include metal or oxidation particles, burrs, cement, and shavings. In other cleaning operations, downhole tubing is cleaned during the displacement from drilling fluids to completion fluids. Common operations used for clean-up operations are slow and inefficient. Specifically, operations used to clean downhole tubing often result in broken scrapers, production downtime, and inefficient cleaning operations.
Accordingly, there exists a need for more efficient debris removal tools for use in downhole cleaning operations.